Method of aging a viscose solution



July 29, 1958 H. ELLING 2,845,416

METHOD OF AGING A VISCOSE SOLUTION Filed Sept. 4. 1953 INVENTOR. HUGO ELL/N6 United States Patent METHOD OF AGING A VISCOSE SOLUTION Hugo Elling, Oberbruch-Grebben, Germany, assignor to American Enka Corporation, Enka, N. C

Application September 4, 1953, Serial No. 378,445

Claims priority, application Germany September 6, 1952 3 Claims. (Cl. 260-218) The present invention relates to a method for making viscose and more particularly to a method for aging viscose. 7

During the production of rayon, viscose is transported by means of pumps into storage tanks in which it remains for several hours for aging. It is known to pump viscose consecutively into several tanks in which the solution is deaerated, for instance in a vacuum. For obtaining a good spinning effect it is of importance that the viscose be made homogenous in a mixing vessel before the spinmng.

The known processes for treating the spinning solution have the disadvantage that due to the high viscosity thereof, portions of the viscose adhere to the walls of the containers, react with the air, and are partly solidified.

Amounts of viscose which have reacted with the air have a gel-like consistency and pass therefore through all filters and through the spinneret producing weak spots in the extruded filament which cause breakage during the further steps of the manufacture of rayon. In the discontinuous operation from single storage tanks according to the known methods, portions of the viscose, known as heels, have to be retained in the tanks in order to prevent entering of air into the conduits. Consequently, when the tanks are filled with the next charge of viscose, the remaining portions of a previous charge'are not only more aged than the new charge, but also contain foam, particularly in the deaeration tanks, such foam also causing disturbances during spinning.

It is one object of the present invention to overcome the disadvantages of the known processes for aging viscose.

It is another object of the present invention to provide a method for aging viscose in such manner that all viscose supplied to the spinning machine is uniformly aged to the same degree.

It is still another object of the present invention to age viscose while preventing contact and reaction of the viscose with an oxidizing medium.

It is a particular object of the present invention to move viscose in a continuous flow through a series of closed containers and connecting conduits which are completely filled with viscose so as to prevent contact of viscose with air during the aging of the viscose.

With these objects in view the present invention mainly consists in a method for aging viscose and comprises the steps of completely filling closed container means with viscose; and retaining said viscose in said container in the absence of an oxidizing gaseous medium until the viscose is aged to the right degree for spinning.

According to a preferred method of the present invention cellulose xanthate is first at least partly dissolved, and then pumped through a series of containers which are completely filled by the solution. In the containers agitating means are provided which stir the viscose. All tanks and all conduits connecting the same are completely filled with the viscose which does not come into contact R 2,845,416 Patented July 29, 1958 2 with the air. while the xanthate is completely dissolved and the viscose aged to the right degree for spinning.

Preferably the viscose is moved in a constant flow during the aging and until reaching the spinneret of the spinning machine.

In order to assurethat all conduit means containing the spinning solution are completely filled and free of air, the supply pumps which press the viscose to the spinneret are supplied with more viscose than is required for the predetermined denier of the produced filament. A return conduit connects the suction side of the supply pump with the last container and since the supply pump can only move a predetermined amount, the surplus of viscose which cannot be absorbed by the supply pump is returned to the last container. The result'of this arrangement is that no coagulated viscose can be formed in the tanks, which in the known arrangement adheres to the walls of the storage tanks at the level of the spinning solution.

The viscose flowing through the aging tanks to the spinning machine is preferably kept by suitable cooling or heating devices H, H at a temperature between 0 degrees centigrade and 45 degrees centigrade, and is allowed to age a time period of 1 to hours. If required, oils and titanium dioxide suspensions are added by suitable mixing means to the viscose while the same is in the aging tanks.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation,.together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing which shows diagrammatically a complete cycle from dissolution of the xanthate to extrusion through spinnerets.

Referring now to the drawing, the xanthate is at least partially dissolved in the containers 10. The pump 11 forces several charges of the solution from containers 10 into the blendingtank 12, in which the solution is mixed by suitable mixing means such as blades 13.

The mixture is continuously deaerated in the vessel 14 by boiling and then is pumped by pump 15 into a conduit system including a first series of storage or aging tanks 16 which are completely filled by the viscose so that all air is expelled therefrom. Additional pumps'17 are pro vided for assuring a continuous flow of the viscose from these tanks. The pumps 11, 15 and 17 are provided with by-pass conduits and valves 18 in order to maintain the respective pressures thereof at a constant level, as is known in the art. The viscose next passes through a 'first filter 19 and is forced by pump 20' into a second series of aging tanks 21. Additional pumps 22, 23 and 24, each of which is provided with a suitable by-pass conduit and valve, force the viscose from tanks 21 through a second filter 25 and a third series of aging tanks 26. If desired, a deaeration by boiling can also be carried out at vessel 27 before the viscose is forced by pump 28 into the third filter 29, from which it passes into the final storage or aging tanks 30. The pump 31 pumps the spinning solution, which has now aged. to the right degree of viscosity for spinning, from the tanks 30 to filter press 32 and to the spinning machine represented by spinnerets 33.

Preferably, the tanks 16, 21, 26 and 30 are provided with agitating and stirring means 34, 35, 36 and 37, respectively. All tanks and conduits are free of air and completely filled by the flowing viscose so that any contact of the solution with an oxidizing medium is prevented. The number of containers of course depends on the time required for aging a particular viscose solution to the right degree of ripeness for spinning.

The first filtration may be carried out immediately after the xanthate has been dissolved, or after the solution has been blended in tank 12. Also, more than one blending tank 12 may be provided for receiving unsuitable batches of viscose. More than one boiling deaeration vessel 14 also may be provided, if found to be necessary or desirable.

According to the preferred embodiment of this invention, as shown in the drawing, the supply conduit 38 of the spinning machine communicates with the return conduits 39, 40. The spinning solution is moved through the conduits of the spinning machine at a speed greater than that of extrusion and is returned to the last tank 30 by means of pump 41 through a pipe 42, in which tank 30 the returned spanning solution is thoroughly mixed with the viscose already present therein. Further closed tanks may be arranged parallel to the tanks 16, 21, 26 and 30 to receive a surplus of viscose solution in the event that the flow of the manufacturing operation is interrupted. The agitating means 34, 35, 36 and 37 preferably are provided at the outermost ends thereof with blades which extend along the inner surface of the tanks and which are closely spaced therefrom so as to remove the viscose from the surface and to prevent a coagulation and adhering of the viscose to the wall. Preferably manometers are provided on the aging tanks so that it is possible to determine whether the required pressure is present, which pressure is maintained by adjusting the output of each pump with respect to the other pumps.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in differing methods for treating viscose before spinning.

While the invention has been illustrated and described as embodied in a method for aging viscose by maintaining a continuous flow of the same through a series of closed containers and conduits which are completely filled with the viscose so as to prevent contact of the same with air, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without'further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. The method of aging a viscose spinning solution while feeding the same to a spinning machine ina deaerated condition through a closed system comprising the steps of maintaining a supply of at least partially tanks and filters, passing the solution alternately through said storage tanks and filters for a sufiicient length of time to insure complete dissolution of the cellulose xanthate and aging of the viscose to the required degree for spinning and pumping the viscose from the storage tanks and filters through still another continuously filled conduit system to a spinning machine.

2. The method of aging a viscose spinning solution while continuously feeding the same to a spinning machine in a deaerated condition through a closed system comprising the steps of maintaining a supply of at least partially dissolved cellulose xanthate in a plurality of dissolving tanks, continuously pumping the solution from the dissolving tanks through a continuously filled conduit system including a blending tank to a deaeration vessel, continuously deaerating the solution, continuously removing the solution from the deaeration vessel and pumping the same through another continuously filled conduit system to a series of completely filled aging tanks, continuously passing the solution through the series of filled aging tanks for a sufficient length of time to insure complete dissolution of the cellulose xanthate and aging of the viscose to the required degree for spinning, continuously filtering the viscose and continuously pumping the viscose from the filtering means through still another continuously filled conduit system to a spinning machine.

3. The method of aging a viscose spinning solution while continuously feeding the same to a spinning machine in a deaerated condition through a closed system comprising the steps of maintaining a supply of at least partially dissolved cellulose xanthate in a plurality of dissolving tanks, continuously blending the solution in a completely filled tank while preventing contact of the same with an oxidizing medium, continuously pumping the solution from the blending tank through a continuously filled conduit system to a deaeration vessel, continuously deaerating the solution, continuously removing the solution from the deaeration vessel and pumping the same to a first series of completely filled aging tanks and filters, continuously passing the solution alternately through said first series of aging tanks and filters, continuously pumping the solution from the first series of tanks and filters to a second deaeration vessel, again continuously deaerating the solution, continuously removing the solution from the second deaeration vessel and pumping the same to a second series of aging tanks and filters, continuously passing the solution alternately through said second series of tanks and filters for a sufiicient length of time to insure complete dissolution of the cellulose xanthate and aging of the viscose to the required degree for spinning and continuously pumping the viscose from the second series of aging tanks and filters through another continuously filled conduit system to a spinning machine.

References Cited in the file of this patent UNITED STATES PATENTS 1,357,946 Borzykowski Nov. 9, 1920 1,357,947 Borzykowski Nov. 9, 1920 1,877,337 Kampf et a1. Sept. 13, 1932 1,895,192 Kampf Jan. 24, 1933 2,087,016 Bradshaw et al. July 13, 1937 2,391,973 Hunter Jan. 1, 1946 2,509,267 Goodwin May 30, 1950 

1. THE METHOD OF AGING A VISCOSE SPINNING SOLUTION WHILE FEEDING THE SAME TO A SPINNING MACHINE IN A DEAERATED CONDITION THROUGH A CLOSED SYSTEM COMPRISING THE STEPS OF MAINTAINING A SUPPLY OF AT LEAST PARTIALLY DISSOLVED CELLULOSE XANTHATE IN A PLURALITY OF DISSOLVING TANKS, PUMPING THE SOLUTION FROM THE DISSOLVING TANKS THROUGH A CONTINUOUSLY FILLED CONDUIT SYSTEM TO A DEAERATION VESSEL WHILE BLENDING THE SAME, DEAERATING THE SOLUTION, REMOVING THE SOLUTION FROM THE DEAREATION VESSEL AND PUMPING THE SAME THROUGH ANOTHER CONTINUOUSLY FILLED CONDUIT SYSTEM TO A SERIES OF COMPLETELY FILLED STORAGE TANKS AND FILTERS, PASSING THE SOLUTION ALTERNATELY THROUGH SAID STORAGE TANKS AND FILTERS FOR A SUFFICIENT LENGTH OF 